George lee anders



(No Model.) G. L. ANDERS.

Telephone Exchange.

No. 239,132. I Patented March 22,1881.

??iii EARTH mgz a m """H 4 2? UNITED STATES PATENT OFFICE.

' GEORGE LEE ANDERS, OF BOSTON, MASSACHUSETTS, ASSIGNOR TO AMERICAN BELLTELEPHONE COMPANY, OF SAME PLACE.

TELEPHONE-EXCHANGE.

SPECIFICATION forming part of Letters Patent No. 239,132, dated March22, 1881.

(No model.)

To all whom it may concern:

Be it known that I, GEORGE L. ANDERS, of Boston, county of Suffolk, andState of Massachusetts, have invented Improvement in Telephone-ExchangeSystems, of which thefollowing description, in connection with theaccompanying drawings, is a specification.

Myinvention relates to telephone-exchange systems, and has for itsobject to facilitate the operation of signaling and communicatingbetween subscribers on different circuits and the operator at thecentral office of the exchange.

In a telephone-exchange system as now commonly arranged the subscriberscircuits radiate out from the central office, and are grounded at theirextremities after passing through one or more subscribers stations, thesaid circuits being also grounded at the central office after eachpassing through an independent indicate ing-instrument.

My invention consists in extending each circuit outward from the centraloffice, and then back thereto by one or more return-branches, passingover a somewhat ditferent path to include additional subscribersstations, which are thus situated at different points throughout theentire length of the subscribers circuit and its return-branches, whichin my system is somewhat similar to two or three adjacent circuits inthe ordinary systems connected to gether at their outward ends insteadof being independently grounded there. The subscribers circuits in myplan thus have both terminals in the centraloflice under the control ofthe operator there, and one of these terminals may be left openwhile-the other is connected with a conductor passing through certainsignaling or telephonic instruments to the ground; or both terminals maybe connected with the said conductor, which, with the said signalingortelephonic instruments, may be made common to a large number of thesubscribers circuits. By this arrangement the subscribers circuits forma series of open branches or loops in the common or union circuit,according as it is connected with one or all of the terminals of eachsubscribers circuit.

In operation, when any subscriber desires to communicate with another hesignals the central office by forming a ground-connection at hisstation, and thus closing the circuit from his station through thecentral instrument, and

if the said instrument be a telephone he immediately makes known hiswishes to the operator, who will be continually listening there. At suchtimes as the operator does not remain listening at the central office avisual or audible signal will be placed in the circuit to at tract hisattention, the said signal being either operated by a magneto'currentgenerated by the subscriber who has closed the circuit, or a battery maybe placed in'circuit with the said instrument, so that the mereoperation of grdunding any of the subscribers circuits will cause thesignal to operate.

When it is desired to call up or signal a subscriber from the centraloffice the terminals of the portion or branch of the said circuitpassing through the station in question are both grounded or connectedwith each other, so as to form a complete closed circuit, in which thesignals at the different stations may be operated in any usual manner.

Figure 1 is a generaldiagram of an exchange system arranged inaccordance with my invention, and Fig. 2 a diagram showing a convenientarrangement of the instruments at each subscribers station.

The subscribers circuits a a I) b c c c d d d are extended out from andback to the cen- 8o tral office in a proper direction to include as manyditl'erent subscribers stations as may be desired, a complete wirecircuit being formed in each instance having both its terminals in thecentral office, instead of the usual circuits 8 5- extended out from thecentral office, and completed by the ground. The said circuits at thecentral office are connected with any convenient switch-board, e, orother means for making connections between the different pairs ofcircuits, and at least one terminal of each of the said circuits isconnected with a conductor, g,common to allot the1n,passing throughsuitable signaling or telephonicinstruments, h or 'i, to the ground,according to the position of 5 the switchj, it being shown in fulllinesin position to cause the circuit to pass through the telephonicinstruments It will be seen that there is thus formed a circuit havingone terminal grounded and a series of open branches mo or loops,according as one or all terminals of the subscribers circuits areconnected to the common or union circuit 9, so that by grounding anypoint on any-of the said branches or loops the circuit is closed fromthe point grounded to the normally-grounded terminal of theunion-circuit, in which all the branches unite.

During the busier portion of the day the common or union circuit 9 willpass through a telephonic instrument, t, and an operator will beconstantly listening there, so that when a subscriber desires acommunication he has merely to make a ground-connection through his owntelephonic instruments, which may be done by the usual automatic orsecrecy switch,

and his circuit is closed through the central instrument, i, at onceenabling him to talk with the central operator and communicate hiswishes without any switching or circuitconnecting operation being neededat the central office. A convenient arrangement of instruments at thesubscribers stations for performing this operation is illustrated inFig. 2, where the line-wire 2 passes to the usual secrecy-switch m,which, when the telephone is hung thereon, as shown, continues thecircuit to wire 3, which includes the signaling-instrument a, of anyusual kind. When the telephone is taken from the hook and the latterturned to one side or the other it operates in the well-known manner toclose the circuit from the line-wire 2 or 3, according to the side it isturned, through the telephone and secondary coil of the transmitter, ifused, to the ground, at the same time breaking the circuit between theline 3 or 2 and switch m, the said line leading to the stations on thecircuit beyond the part thereof thus connected with the central officebeing left open, as indicated at b, circuits 0!, and d, Fig. 1. Thisoperation of the switch mis sufficient to put the subscriber incommunication with the central office if the switch j be properly placedto pass the circuit through the telephone 2', and when the signalbell his in circuit will cause the current of the battery B to flow through itand cause it to operate, when the attendant will turn the switch j andbring the telephone '5 into circuit, as before described.

When desired to signal or call up a subscriber from the central officeone terminal of his circuit is either grounded or connected throughsuitable signal-transmitting instruments to the other terminal, asillustrated in the circuit b, where the terminal of the portion b isconnected by plug 7 with the circuit a", while the portion b stillremains connected with the circuit 9 and the ground. The circuit b b isthus closed through the subscribers station, and thesignaling-instrument, of any usual construction, at the said station maybe operated in the usual manner, as by the battery B and keys 2?. Thecircuit 1" through the signal operating apparatus may either be groundedto thus complete the circuit to the grounded terminal of the wire 9through the the branch at.

gether for communication between the different subscribers stationsthereonin anyusual manner, as my novel arrangement of the circuits willmake'no difference in this particular.

The subscribers circuits may either have one endiepen and theotherjoined to the unionstrip g, as indicated by the plugs 8 on theswitch-board, Fig. 1, in connection with circuits a a b b, or all theterminals may be connected therewith, as shown in the circuits 0 0 c d dd, as in either case a complete circuit will not be formed until somepoint is grounded on some portion of a subscribers circuit.

In case one terminal only is connected with the union-circuit g, theswitch at must be properly turned to connect the ground with the branchor portion of the subscribers circuits that is connected with the saidunion-circuit; but if all the terminals are connected with the saidunion-circuit, as shown at 0 c c, the ground may be connected with anypart of the said circuit, as the circuit may be closed from thesubscribers station to the central office over either branch. Forexample, the station at 6 on circuit a a might have been connected overthe branch at instead of, as shown, over When no portion of the circuitis in use the subscriber will use that portion of the circuit passingthrough the least number of stations in its course to the centraloffice.

When one terminal is to be left open it may be desirable to distinguishit from the one normally kept connected with the union-circuit g. Thismay be done by making the strips of the switch-board of different color,as indicated at the left thereof in Fig. l, where the branch to benormally connected with the union-circuit g has a black stripe. In thecircuit a a the branch (1 has been disconnected from and the one aconnected with the unioncircuit 9 while the communication of thesubscriber at station 6 is going on.

When two subscribers on different circuits are to be connected, as atthe station 6 on circuits d a, that portion of the circuit which passesthrough the smaller number of stations in reaching the central oficeshould be disconnected at the central office from the union-circuit gand connected with the other subscribers circuit, as shown, and if theplan of having only one terminal normally connected with the saidunion-circuit g is followed, and this terminal is disconnectedtherefrom, then another terminal should be connected, as shown, by theplug 8 on circuit a, so that at any time all the subscribers on acircuit except those lying between the station communicating and thecentral office on the branch connecting these points will have access tothe central office as, for example, on circuit a a only the statoo tion10 willbe cut off while the one 6 is connected, all the others, as 11,12, &c., having access to the central office over the branch at, nowconnected with the union-circuit 9. By this arrangement of circuits theexchange is operated with much greater facility than by the arrangementnow commonly in use, and

the circuits are more completely in control of the station to be calledis on the former or latter of the said branches, and for calling asubscriber on the main branch 0 either of the branches 0 or 0 may beclosed.

The circuits may be ramified out even farther without departing from myinvention, provided that all the connected branches be brought back tothe central office, and a complete circuit is afforded from any point inthe said branches through the different subscribers stations to thecommon circuit passing through thecentral instrument. seen by thisarrangement only one signal, h, is needed for a large number ofcircuits, while by the common plan a signal is needed for each circuit.

In the present plan two subscribers on the same circuit can communicatetogether over the portion of the circuit lying between their stations onthe side away from the central office, or by connecting the terminals atthe cen tral office their circuit can be completed in the oppositedirection from their stations through the central office.

I claim- 1. In a telephone-exchange system, a series of subscriberscircuits, each extend ed out from and back to the central ofiice, thusforming It will be a complete wire circuit passing through subscribersstations at different points throughout its entire length, and havingits terminals in the said central office,'in combination with a commonor union circuit connected with each of the said circuits and grounded,and suitable signaling or telephonic instruments in the saidunion-circuit, whereby making a groundconnection at any point on any ofthe said subscribers circuits will at once make a closed circuit fromthe said point through the instruments in the union-circuit at thecentral ofiice, substantially as and for the purpose described.

2. In a telephone-exchange system, a subscribers circuit having oneterminal normally grounded at the central office and two or morebranches extended back to the central office, whereby making aground-connection at any point on the said circuit or its branchescloses the circuit therefrom to the normally-grounded terminal at thecentral office, and by grounding or connecting any two of the saidterminals a closed circuit is formed through the corresponding branchfor signaling from the central office, substantially as described.

3. In a telephone-exchange system, a series of subscribers circuitswholly metallic, and having all their terminals at the central office,combined with a receiving-signal or telephonic apparatus in a portion ofa circuit grounded on one side of the said instruments and normallyconnected with one or all the terminals of each of the said subscriberscircuits, but adapted to be readily disconnected therefrom,

and signal-operating mechanism in a portion of a circuit grounded orconnected with the circuit containing the receiving-instruments, andadapted to be connected with any of the terminals of the saidsubscribers circuits, the whole to operate for signaling andcommunicating between the subscribers stations and central office,substantially as described.

In testimony whereof I have signed my name to this specification in-thepresence of two subscribing witnesses.

GEORGE LEE ANDERS.

Witnesses: J os. P. LIVERMORE, ARTHUR REYNOLDS.

